Specific interactions of cells within the extracellular matrix are critical for the normal function of organisms. Alterations of the extracellular matrix are carried out by a family of zinc-dependent endopeptidases called matrix metalloproteinases (MMPs). The alterations are carried out in various cellular processes such as organ development, ovulation, fetus implantation in the uterus, embyiogenesis, wound healing, and angiogenesis. Massova, I.; Kotra, L. P.; Fridman, R.; Mobashery, S. FASEB J. 1998, 12, 1075; Forget, M.-A.; Desrosier, R. R.; Béliveau, R. Can. J. Physiol. Pharmacol. 1999, 77, 465–480.
MMPs consist of five major groups of enzymes: gelatinases, collagenases, stromelysins, membrane-type MMPs, and matrilysins. The activities of MMPs in normal tissue functions is strictly regulated by a series of complicated zymogen activation processes and inhibition by protein tissue inhibitors for matrix metalloproteinases (“TIMPs”). Forget, M.-A.; Desrosier, R. R.; Béliveau, R. Can. J. Physiol. Pharmacol. 1999, 77, 465–480; Brew, K.; Dinakarpandian, D.; Nagase, H. Biochim. Biophys. Acta 2000, 1477, 267–283. Westermarck, J.; Kahari, V. M. FASEB J. 1999, 13, 781–792. Excessive MMP activity, when the regulation process fails, has been implicated in cancer growth, tumor metastasis, angiogenesis in tumors, arthritis and connective tissue diseases, cardiovascular disease, inflammation and autoimmune diseases. Massova, I.; Kotra, L. P.; Fridman, R.; Mobashery, S. FASEB J. 1998, 12, 1075; Forget, M.-A.; Desrosier, R. R.; Béliveau, R. Can. J. Physiol. Pharmacol. 1999, 77, 465–480; Nelson, A. R.; Fingleton, B.; Rothenberg, M. L.; Matrisian, L. M. J. Clin. Oncol. 2000, 18, 1135.
Increased levels of activity for the human gelatinases MMP-2 and MMP-9 have been implicated in the process of tumor metastasis. Dalberg, K.; Eriksson, E.; Enberg, U.; Kjellman, M.; Backdahl, M. World J. Surg. 2000, 24, 334–340. Salo, T.; Liotta, L. A.; Tryggvason, K. J. Biol. Chem. 1983, 258, 3058–3063. Pyke, C.; Ralfkiaer, E.; Huhtala, P.; Hurskainen, T.; Dano, K.; Tryggvason, K. Cancer Res. 1992, 52, 1336–1341. Dumas, V.; Kanitakis, J.; Charvat, S.; Euvrard, S.; Faure, M.; Claudy, A. Anticancer Res. 1999, 19, 2929–2938. As a result, select inhibitors of MMPs (e.g., MMP-2 and MMP-9) are highly sought.
Several competitive inhibitors of MMPs are currently known. These inhibitors of MMPs take advantage of chelation to the active site zinc for inhibition of activity. Because of this general property, these competitive inhibitors for MMPs are often toxic to the host, which has been a major impediment in their clinical use. Greenwald, R. A. Ann. N.Y. Acad. Sci. 1999, 878, 413–419; (a) Michaelides, M. R.; Curtin, M. L. Curr. Pharm. Des. 1999, 5, 787–819. (b) Beckett, R. P.; Davidson, A. H.; Drummond, A. H.; Huxley, P.; Whittaker, M. Drug Disc. Today 1996, 1, 16–26.
Gelatinases have been shown to function in both female ovulation and inplantation of zygotes in the womb. The female contains a pair of gonads, a system of ducts and chambers to conduct the gametes as well as to house the embryo and fetus, and external genitalia that facilitate reproductive function. The female gonads, the ovaries, lie in the abdominal cavity below most of the digestive system. Each ovary is enclosed in a tough protective capsule and contains many follicles. A follicle consists of one egg cell surrounded by one or more layers of follicle cells, which nourish and protect the developing egg cell. All of the 400,000 follicles a woman will ever have are formed at birth. Of these, only several hundred will be released during the woman's reproductive years. After puberty, one (or rarely two or more) follicle matures and releases its egg during each menstrual cycle. The cells of the follicle also produce the primary female sex hormones, the estrogen. When ovulation occurs, the egg is expelled from the follicle (much like a small volcano), and the remaining follicular tissue grows within the ovary to form a solid mass called the corpus luteum. The corpus luteum secretes progesterone, the hormone of pregnancy, and additional estrogen. If the egg is not fertilized, the corpus luteum degenerates and a new follicle matures during the next cycle.
The female reproductive system is not completely closed, and the egg cell is expelled into the abdominal cavity near the opening of the oviduct, or fallopian tube. The oviduct has a funnellike opening, and cilia on the inner epithelium lining the duct help collect the egg cell by drawing fluid from the body cavity into the duct. The cilia also convey the egg cell down the duct to the uterus, commonly called the womb. The uterus is a thick, muscular organ shaped much like an upside-down pear. It is remarkably small; the uterus of a woman who has never been pregnant is about 7 cm long and 4–5 cm wide at its widest point. The unique arrangement of muscles that make up the bulk of the uterine wall allow it to expand to accommodate a 4-kg fetus. The inner lining of the uterus, the endometrium, is richly supplied with blood vessels.
The pattern of hormone secretion controlling female reproduction differs strikingly from the male pattern, reflecting a cyclic nature of female reproduction.
Two different types of cycles occur in female mammals. Humans and many other primates have menstrual cycles, whereas other mammals have estrous cycles. In both cases, ovulation occurs at a time in the cycle after the endometrium has started to thicken and become more extensively vascularized, which prepares the uterus for the possible implantation of an embryo.
The menstrual cycle averages 28 days, but only about 30% of women have cycle lengths within a day or two of the statistical 28 days. Cycles vary from one woman to another, ranging from about 20 to 40 days. In some women the cycles are usually very regular, but in other individuals the timing varies from cycle to cycle.
Paralleling the menstrual cycle is an ovarian cycle. It begins with the follicular phase, during which several follicles in the ovary begin to grow. The egg cell enlarges and the coat of follicle cells becomes multi-layered. Of the several follicles that start to grow, only one usually continues to enlarge and mature, while the others degenerate. The maturing follicle develops an internal fluid-filled cavity and grows very large, forming a bulge near the surface of the ovary. The follicular phase ends with ovulation when the follicle and adjacent wall of the ovary rupture, releasing the egg cell. The follicular tissue that remains in the ovary after ovulation is transformed into the corpus luteum, an endocrine tissue that secretes female hormones during what is called the luteal phase of the ovarian cycle. The next cycle begins with a new growth of follicles.
Contraception literally means “against taking,” in this case, the taking in of a child. The term has come to mean preventing a pregnancy through one of several methods. These methods fall into three main categories: (1) preventing the egg and sperm from meeting in the female reproductive tract, (2) preventing implantation of a zygote, and (3) preventing the release of mature eggs and sperm from the gonads.
Besides complete abstinence, the methods that prevent release of gametes are the most effective means of birth control. Chemical contraception (birth control pills) have failure rates of less than 1%, and sterilization is nearly 100% effective. Birth control pills are combinations of a synthetic estrogen and a synthetic progestin (progesterone-like hormone). These two hormones act by negative feedback to stop the release of GnRH by the hypothalamus and FSH (an estrogen effect) and LH (a progestin effect) by the pituitary. By blocking LH release, the progestin prevents ovulation. As a backup measure, the estrogen inhibits FSH secretion so no follicles develop. Chemical contraception has been the center of much debate, particularly because of the long-term side effects of the estrogens. No solid evidence exists for cancers caused by the pill, but cardiovascular problems are a major concern. Birth control pills have been implicated in blood clotting, atherosclerosis, and heart attacks. Smoking while using chemical contraception increases the risk of mortality tenfold or more. Campbell, N.; Biology, 2nd Ed., Benjamin/Cummings Publ., Redwood City, La., 1990.
Accordingly, there is a current need for inhibitors of MMPs. Such inhibitors would be useful to treat or prevent cancer, tumor metastasis, angiogenesis in tumors, contraception, arthritis and connective tissue diseases, cardiovascular disease, inflammation or autoimmune diseases. Preferred inhibitors may exhibit selectivity for one or more specific MMPs than known competitive inhibitors. In addition, additional methods that prevent the release of gametes are needed. Suth methods will preferably not include negative long-term side-effects.